Journal
NANO ENERGY
Volume 57, Issue -, Pages 703-710Publisher
ELSEVIER
DOI: 10.1016/j.nanoen.2019.01.003
Keywords
Thermoelectric; MnTe; Bond covalency; Hierarchical architecture; Alkaline dopants
Categories
Funding
- National Natural Science Foundation of China [51572098, 51632006, 51772109, 51872102]
- Fundamental Research Funds for the Central Universities [2018KFYXKJC002]
- Open Fund of State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology [2016-KF-5]
- Graduates' Innovation Fund, Huazhong University of Science and Technology [5003110006]
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Pb-free MnTe has recently been discovered to be a promising thermoelectric material because of its low toxicity and eco-friendly nature. Here, we have proposed and demonstrated an effective approach to boost the electrical transport of MnTe compound via reinforcing bond covalency through M/S (alkaline dopants M = Li, Na, and K) co-doping. By means of this strategy, the electrical conductivity was significantly improved owing to the increasing carrier concentration and mobility, which is attributed to the decreasing electronegativity difference vertical bar chi(Te)-chi(M)vertical bar as M going from K to Na to Li. The single Kane band model enables a reliable assessment of their temperature-dependent electrical properties, further suggesting that the bipolar effects at high temperature can be effectively suppressed by reinforcing bond covalency. Moreover, beneficial from alkali doping and sulfur substitution, the lattice thermal conductivities have been sharply reduced to amorphous limit through intensive phonon scattering induced by the multiscale hierarchical architecture such as the nanostructures, coherent grain boundary and high-density dislocations, etc. As a result, a record-high peak zT of similar to 1.3@873 K, corresponding to a calculated engineering output power density similar to 1.46 Wcm(2) and leg efficiency eta similar to 8.4%, has been achieved in the Li/S co-doped (Mn1.04Li0.02Te0.99S0.01) sample. This work provides a referential route to enhance electrical properties via synergistically improving carrier concentration and mobility by reinforcing bond covalency, impelling the potential applications of MnTe-based thermoelectric materials as a robust candidate for waste heat recovery.
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